Usually, after a freezing and refrigerating device, such as a fridge or the like, operates for a certain period, the surface of its evaporator frosts. The frost affects the heat exchange between the evaporator and the air inside the fridge and reduces the refrigerating efficiency of the evaporator. Therefore, defrosting must be performed after the fridge operates for a certain period.
In the prior arts, usually defrosting of an evaporator is performed by heating. However, a lot of vapor is generated during defrosting and may enter the storage compartment of the fridge via air inlets. In this case, on one hand, heat contained in the hot air is wasted; on the other hand, the temperature in the storage compartment rises, affecting the freshness and freezing time of food.